This invention is directed to N/C machine systems and, more particularly, to systems for improving the productivity of N/C machines.
Typically, a numerically controlled (N/C) machine tool area consists of a large number of closely spaced machine tools. Normally, the machines are positioned along aisleways with various size machines being intermixed. In most cases, the machines are constructed such that the machine operating station is located at some distance from the adjacent aisle. Since the operator is literally surrounded by machinery, visibility of, or by, the operator is very difficult. Various shop support personnel (i.e., supervisors, area men, relief operators, tool kitters and maintenance personnel) are provided to sustain the production of the N/C machines. However, due to the position of the machine operating stations, an operator cannot easily communicate with shop support personnel. And, rarely, are support personnel present when they are needed. Because of this difficulty, in the past, when support or assistance was required, an operator had two options. He could wait at his machine operating station until the required support personnel appeared; or, he could turn off his machine, leave this station, and seek the required person or service. In either case, the end result was reduced productivity because the chip cutting time of the machine was curtailed. In one sampling study of an N/C machine tool area consisting of 81 N/C machines, it was found that 5.4% of an operator's time was spent non-productively away from his machine looking for support personnel. Another 3.1% was spent non-productively waiting for machine support personnel. Obviously, the loss in available machine hours for a machine tool area of any size is substantial.
Another problem area that is inherent in the management of large concentrations of N/C machine tools is the lack of real time knowledge of machine status, and the difficulty of solving manufacturing problems caused by this lack of real time knowledge. The lack of such knowledge is generally the result of communication difficulties. In this regard, the ambient noise level in a machine tool environment is often at or near 90 decibels. Thus, voice communication (e.g., telephone, etc.) is very difficult. Plant paging systems are essentially ineffective and pocket radio paging devices simply do not work satisfactorily.
Another problem, which is also of a communication nature, relates to the difficulty in providing management with detailed information about the operation of large N/C machine tool manufacturing complexes. In the past, often paper and pencil methods of data collection have been used to gather historical data. Reports are usually produced on a weekly or monthly basis. Because the report information is historical rather than real time, problem solving is more difficult and time consuming than it would be if real time information were available. Routine problems have often taken hours to solve, and difficult problems have taken days.
It will be appreciated that all of the foregoing problems contribute to a decrease in the chip cutting time of the N/C machine. Chip cutting time is, obviously, the amount of time that the machine is actually producing parts and, thus, is a measure of the productivity of a machine. Lack of rapid and quick communication between support personnel and machine operators; and lack of real time communication between management and machines, both contribute to a decrease in chip cutting time and, thus, productivity.
In an attempt to alleviate the foregoing problems, various types of production monitoring control systems have been proposed by the prior art. Many such systems include an operator input module located at each N/C machine. The modules allow the operators and/or management, maintenance or other personnel to electronically advise a control station of a wide variety of information related to productivity and/or that certain assistance is needed. In accordance with this information, the control station automatically or personnel manually, using pencil and paper methods, record the status of machine operation. In addition, if the operator needs assistance, control station personnel contact the necessary support personnel and direct him (them) to the location of the machine needing assistance.
While production monitoring and control systems of the foregoing nature have assisted in reducing chip cutting time when compared with N/C machine stops having no production monitoring control system, prior art production monitoring control systems have a number of disadvantages. For example, as noted above, the central location personnel, after a call for assistance arrives, must locate the necessary shop personnel. If such personnel, as is often the case, are located in the machine shop area, making contact is often difficult and time consuming. Shop and personnel radio or audio paging device generally do not work satisfactorily, due to shop noise and electromagnetic interference. Hence, in many instances, the desired person or persons must be physically located by the central station operator or an assistant. Because such methods of locating support personnel are time consuming, chip cutting time is reduced.
Another problem with prior art production monitoring control systems is the restricted nature of the types of assistance calls that can be made. In many cases only a handful of different call codes can be produced by an operator's call module. Hence, the operator is restricted as to the type of information he can transmit to the control room, whereby, often a supervisor must first go to the machine to more precisely determine the type of assistance needed, before the assistance can be sought and provided.
Another problem with prior art production monitoring control systems is their use of somewhat sophisticated electrical systems for accurately transmitting data from a shop area to a control station. More specifically, as will be appreciated by those skilled in the N/C machine tool art, electromagnetic interference (EMI) is usually high in large N/C machine manufacturing complexes. The existence of high EMI levels tends to rapidly deteriorate signals passing through non-shielded cables. Thus, simple twisted cable cannot be used, particularly where cable runs are long, without a significant loss of information. In the past, either shielded cables and/or been less electronic circuitry has been utilized to locate signal information contained in the cable noise created by EMI. Obviously, either or both of these solutions are expensive and, thus, undesirable.
Another disadvantage of prior art production monitoring control systems (and also applicable to many other data transmission systems) relates to the power consumed during data transmission. In the past, data has often been transmitted using push-pull current techniques. The problem with current data transmission is that current in the milliampere range is normally required. On the other hand voltage data transmission only requires current in the microampere range, resulting in a power reduction factor of approximately 1000. One of the primary reasons for current data transmission is that, in the past, voltage data transmission has been less noise immune, that current data transmission. Obviously from a power consumption standpoint it is desirable to overcome this disadvantage.
Therefore, it is an object of this invention to provide a new and improved system for enhancing the chip cutting time of N/C machines.
It is also an object of this invention to provide a system that provides for the rapid and accurate transmission of operator assistance requests to the personnel trained to provide the requested assistance.
It is a further object of this invention to provide a new and improved N/C machine monitoring system that provides for the rapid transmission of assistance calls from a machine operator to the individual or individuals trained to provide the desired assistance, even though such individual or individuals are located in areas where they cannot be readily contacted by audio devices.
It is a still further object of this invention to provide a new and improved means for rapidly and accurately transmitting data in a voltage manner over relatively long cables located in an environment wherein a substantial amount of electromagnetic interference exists, without a substantial deterioration of the transmitted data occurring.
It is yet another object of this invention to provide a system for use in an N/C machine tool environment that assists in rapidly providing operator assistance while providing on a real time basis information for use by management.